In co-pending Ser. No. 746,092, filed June 18, 1985, now U.S. Pat. No. 4,673,459 (the disclosure of which is hereby incorporated by reference herein) a radial configuration evaporator structure is disclosed. Such a structure is very effective for performing its desired evaporating functions, evaporating liquor flowing as a film down the exteriors of the heating element plates. While the evaporator illustrated and described in said co-pending application is functionally very advantageous, it is desirable to be able to produce the evaporator at a lower cost.
According to the present invention, an evaporator is provided which is functionally comparable to the evaporator disclosed in said co-pending application, yet can be produced at a lower cost. The best structural feature that allows low cost production of the evaporator according to the present invention is the utilization of a thin skin as a side wall of the evaporator vessel, such a side wall preferably being provided by a continuous circumferential piece of stainless steel approximately 1/8 th of an inch thick. The wall also cooperates with the pairs of parallel dimpled plates defining each of the heating elements, to cooperate with the plates to define a fluid tight interior volume for each of the heating elements. Such a structure compares to a 1/2 inch thick stainless steel body shell of an evaporator such as disclosed in said co-pending application. The heating elements themselves become a part of the structure which supports the skin for internal and external pressure as well as the dome of the vessel.
At the top of the heating elements, a liquor distributing means is provided. Such a means provides liquor that is to be evaporated by falling as a film down the exteriors of the plates of the heating elements. Such a distributing means preferably is provided by a perforated plate which is supported by the heating elements and a donut-shaped liquor introduction means disposed above the perforated plate for uniformly distributing introduced liquor around the plate. A vapor outlet for the evaporator is concentric with the radially disposed heating elements, and with the liquor distribution means, with a vapor outlet provided concentrically at the top of the vessel.
The vessel also includes a bottom portion which may be continuous with the circumferential wall of the vessel. The heating elements are supported at the bottoms thereof by a ring, the ring supported on the bottom of the vessel by a vertical axis tube. The tube walls have means defining a plurality of through-extending holes therein to allow liquor circulation. A transfer liquor outlet and a circulation liquor outlet are provided at the bottom of the vessel.
Heating fluid is introduced into the fluid tight interior volumes of the heating plates, preferably by an annular header adjacent the tops of the elements. A venting means is also provided for allowing spent heating fluid (e.g. steam) to escape from the interiors of the heating elements, the venting means preferably also provided as an annular header disposed adjacent the bottoms of the heating elements.
It is the primary object of the present invention to provide an evaporator having significant cost savings while still performing functionally to effectively evaporate introduced liquor. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.